Preparation and dispersion stability of aqueous metal oxide nanofluids for potential heat transfer applications: a review of experimental studies

Journal of Thermal Analysis and Calorimetry - Nanofluids have recently attracted attention of many researchers due to their growing potential applications in heat transfer devices. They possess...     

An Experimental Model to Simulate Arterial Pulsatile Flow: In Vitro Pressure and Pressure Gradient Wave Study

A new experimental model developed to simulate arterial pulsatile flow is presented in this paper. As a representative example, the flow characteristics and the properties of brachial artery were adopted for the purpose of this study. With the physiological flow of the human brachial artery as the input, the pressure and pressure gradient waves under healthy and different scenarios mimicking diseased conditions were simulated. The diseased conditions include the increase in blood viscosity (reflecting the elevation of hematocrit), stiffening of the arterial wall, and stiffening of the aortic root as the coupling between the heart and arterial tree, presented by the Windkessel element in the setup. Each of these conditions resulted in certain effects on the propagation of the pressure and pressure gradient waves, as well as their patterns and values, investigated experimentally. The results suggest that the pressure wave dampens at arterial sites with higher hematocrit, while the stiffening of the Windkessel element elevated the diastolic pressure, and lowered the pressure drop, similar to the results observed by stiffening the arterial wall. Based on these results, it is hypothesised that the cardiovascular system may not function within the minimum energy consumption criterion, contrary to some other physiological functions.     

Wγγ production as a test of three- and four-gauge-boson couplings at LHC and SSC

The reaction pp→W^±γγX is considered at centre-of-mass energies √s = 16 and 40 TeV, including anomalous three- and four- gauge-boson couplings κ and λ. Limits are obtained on these quantities by comparison with the standard model.     

Finite integration method for partial differential equations

A finite integration method is proposed in this paper to deal with partial differential equations in which the finite integration matrices of the first order are constructed by using both standard integral algorithm and radial basis functions interpolation respectively. These matrices of first order can directly be used to obtain finite integration matrices of higher order. Combining with the Laplace transform technique, the finite integration method is extended to solve time dependent partial differential equations. The accuracy of both the finite integration method and finite difference method are demonstrated with several examples. It has been observed that the finite integration method using either radial basis function or simple linear approximation gives a much higher degree of accuracy than the traditional finite difference method.     

The two-jet angular distribution probing virtual exotics at hadron colliders

Heavy virtual exotics, affecting the QCD quark-scattering amplitudes, can best be probed by the normalized two-jet angular distribution at the LHC, the SSC and the Fermilab Tevatron. As typical examples we considerSU(3) _L SU(3) _R axigluons andE ₆ diquarks compared to the more familiar quark effective contact terms. We propose optimal jet pseudorapidity and invariant-mass cuts in order to enhance the signal at the future colliders. The discovery limits thus obtained, are studied in terms of energy and luminosity for each machine, comparatively.Supported in part by a CEC Science Program (Contract no. SC1-CT91-0729)     

Oxidation investigation of nickel nanoparticles

This work reported an experimental investigation of complete oxidation of nickel nanoparticles using simultaneous thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Nickel nanoparticles and their elemental compositions were characterized by Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The oxidation experiments were performed under isoconversion conditions for seven heating rates, varying from 2 to 20 K min(-1), with temperatures up to 1000 degrees C. The experiments revealed unique oxidation behaviour of nickel at the nanometre scale, such as early oxidation and melting phenomena, variable activation energies and different oxidation kinetics between low and high conversion ratios. Unlike its bulk counterpart where the activation energy is a constant, the activation energy of nickel nanoparticles depended on the conversion ratio, ranging between 1.4 and 1.8 eV. The oxidation kinetics of nickel nanoparticles changed from the classical diffusion controlled mechanism to a pseudo-homogeneous reaction as conversion ratios were over 50%. The oxidation mechanisms of nickel nanoparticles were further discussed and future studies to enhance understanding were identified.